The present invention relates generally to a pressure relief valve and, more particularly, to a multi-function pressure relief valve having a moveable seat and a movable needle to both vent and release excess pressure in a fuel vapor separator.
Pressure relief valves are designed to protect a pressurized system against excessively high or low pressure in the event of positive or negative excursion of the system pressure. They are required to open at a predetermined system pressure, to discharge or admit air or another fluid so as to prevent the system pressure from exceeding a specified upper or lower pressure limit, and to automatically reclose after a normal system pressure has been restored. These pressure relief valves have numerous applications in process, petrochemical, and automotive industries.
Vapor release valves are designed to allow a vessel to become filled by a fluid by venting air or another vapor out of a vessel that is displaced by the incoming fluid. Nearly every vessel that stores a fluid must have some type of venting arrangement to allow the fluid to enter the vessel without being restricted by vapor within the vessel. The venting system operates to expel the vapor as the fluid enters the vessel. Some of these systems are not required to be pressurized. The venting arrangement for some of these unpressurized systems can be as simple as an open vent line located on the top of the vessel. Other unpressurized systems may have a check valve in the vent line to prevent return vapor flow into the vessels, and still other systems may have a vapor recovery system to return the fluid vapors back to the vessel while expelling vapor. Still other systems are pressurized and must incorporate measures to expel air via a venting system that allows the vessel to become pressurized after venting. Vapor release valves used in pressurized systems typically include a needle and seat arrangement wherein the needle is operated by a float assembly and engages and disengages a stationary seat at the top of the vessel. When the vessel is empty, or the fluid level in the vessel is low, the float pulls the needle into an open position to allow venting. As the fluid fills the vessel, the float moves upward and closes the needle against the seat when the vessel is full as dictated by the float level.
One application for pressure relief valves and/or vapor release valves is in fuel vapor separators. Fuel vapor separators are often used in fuel delivery systems of internal combustion engines to remove entrained vapor from fuel. Heat build up in an engine can adversely affect the engine""s fuel delivery system by causing the fuel to become vaporized before it is introduced into the engine""s combustion chamber. The vaporized fuel interferes with proper engine combustion and, consequently, with engine power and performance. Pressure vessels, such as fuel vapor separators, are known for reducing or eliminating vaporized fuel in the fuel delivery system. The fuel vapor separator includes a housing where fuel is passed through and in which vapor is allowed to separate from the liquid fuel. During filling of the system, the vapor from the fuel is vented from the separator through a vapor release valve, which is usually of the movable needle and stationary seat type that is operated by a float assembly as previously described. After venting is complete, the vapor release valve closes upon consequent filling of the separator with liquid fuel.
Some fuel vapor separators may incorporate a separate pressure relief valve to exhaust excess pressure from the systems after the separator is pressurized. The need for pressure relief valves in fuel vapor separators is especially evident in outboard marine engines. Most fuel vapor separators have coolant passages to maintain the fuel temperature in the fuel delivery system at an acceptably low value. Unlike most internal combustion engines that have closed coolant systems, outboard marine engines instead utilize the benefit of fresh water supplied by the lake or other waterway in which they are used to cool the engine. The water is continually circulated past the fuel vapor separator to cool the fuel in the separator. However, a problem can arise with this type of arrangement when the engine shuts down. The typical fuel vapor separator is mounted on or near the engine to maintain a consistent fuel temperature which increases engine performance and economy. Once the engine is shut down, the coolant water drains from the engine and the fuel separator. Under certain conditions, as the water is draining from the separator after the engine is shut down, the water can heat up rapidly and vaporize due to the fact that the engine is still hot and the water is no longer circulating through the system. This can cause the fuel inside the fuel vapor separator to also heat up and expand. Although fuel vapor separators are designed to withstand a certain pressure differential, as with any design, there are always limits. Accordingly, a pressure release valve may be placed in the separator to accommodate extreme conditions where the temperature differential between the water and engine exceed the design parameters and create a pressure differential in the separator that exceeds the design parameters. Such a pressure release valve can then expel vapor and/or fuel from the separator until the pressure and temperature differentials are normal. The use of both a vapor release valve and a pressure relief valve in the same system significantly adds to the cost and complexity of the system.
In view of the aforementioned, it would be desirable to design a single multi-function valve that allows both vapor to vent from a fuel vapor separator or other system in response to changing fluid levels as well as excess pressure to be relieved within the system.
The present invention solves the aforementioned problems by providing a multi-function valve that has a movable seat and a movable needle, each providing a separate function. Specifically, multi-function valve opens and closes in response to both (1) changing fluid level in a fuel vapor separator or other pressurizable system, and (2) excess vapor pressure within the vapor fuel separator.
The valve has a valve body with an inlet port and an outlet port. A movable needle is disposed in the inlet port of the valve body and is controlled by a float attached to the needle. The float moves the needle between (1) an open, venting position when the float is in a lowered position in response to low fluid levels in the chamber caused by the presence of air or fuel vapor in the chamber, and (2) a closed position when the float is in a raised position in response to elevated fluid levels in the chamber. The multi-function valve also includes a movable seat located in the outlet port of the valve body. The movable seat is biased to a closed position in which it contacts the needle and is responsive to excess pressure in the chamber to an open, pressure relief position which disengages the seat from the needle and allows pressure relief from the internal chamber. In one embodiment, the multi-function valve is used in a fuel separator of an outboard marine engine.
Other various features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings.